An Open Label Study of Itacitinib Administered Orally in Patients With Myelofibrosis

Inclusion Criteria:

- Must be diagnosed with PMF, PPV-MF or PET-MF as confirmed by bone marrow biopsy.

- Must score at least 1 point on the Dynamic International Prognostic Scoring System
(DIPSS) for prognostic risk factors and have peripheral blast count <10% at both
Screening and Baseline hematology assessments.

- Subjects must discontinue all drugs used to treat underlying MF disease no later than
Day -14.

- Subjects must have hemoglobin value >/= 8.0g/dL and be willing to receive blood
transfusions, have a platelet count >/=50x10^9/L and absolute neutrophil count (ANC)
>/= 1x10^9/L.

- Subjects must have palpable spleen or history of splenectomy

- Active symptoms at the screening visit

Exclusion Criteria:

- Women who are pregnant or breastfeeding, and men and women who cannot comply with
requirements to avoid fathering a child or becoming pregnant, respectively.

- Subjects with impaired liver function, end stage renal disease on dialysis or
clinically significant concurrent infections requiring therapy.

- Subjects with unstable cardiac function or invasive malignancies over the previous 2
years except treated basal or squamous carcinomas of the skin, completely resected
intraepithelial carcinoma of the cervix and completely resected papillary thyroid and
follicular thyroid cancers.